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Survival of a Species
The following transcript is from the 2019 edition of the Broadcaster, an official visitor's guide to the Broads National Park in Norfolk. Survival of a Species You may well have heard that the swallowtail, the United Kingdom's largest and one of its rarest butterflies, is only found in the Broads, but do you know why? The swallowtail was once found in a scattering of wetlands across southern England but the increased draining of wetlands for agriculture in Victorian times saw it retreat to the Broads, where it has become slightly smaller and is now a subspecies unique to the Broads; Papilio machaon britannicus. It is one of sixty-six species in the Broads of conservation concern that are found almost nowhere else in the United Kingdom. But it was not just draining wetlands that caused problems. During the twentieth century, especially after the second world war, management of the remaining fens declined and much of this butterfly's habitat was lost. Today, with active management of fens, where reed and sedge are cut every four to seven years to allow other plants to grow, the future for the swallowtail looks brighter. But why and for how long? The swallowtail requires sites with a growth of tall milk parsley plants - in the Broads, it has become dependent on this one food plant for its caterpillar. Milk parsley depends on the correct water level and management to prevent scrub growth. Sea level rise, which would result in higher water levels and an increase in salinity, would affect the growth of milk parsley. The Broads fens are areas of wet, marshy ground, situated on peat soils and regularly inundated with water either from the rivers or groundwater sources. Traditional fen harvesting plays an important part in the survival of the swallowtail. Historically, fens were managed and harvested for their natural produce: reed and sedge for thatching, and marsh hay and litter for animal bedding. With the reduced demand for these products, the management of many fens ceased and the process of natural succession was allowed to continue, resulting in a gradual loss of open fen to willow, alder scrub, and woodland. Here in the Broads, because many fens remained undrained and because commercial reed cutting and active conservation management work have kept large fen areas free of scrub, there is still milk parsley on nearly a quarter of the peat fen and there are good numbers of swallowtails too. However, if salty and higher water levels resulting from climate change destroy the larval food plant, the Broads swallowtails will not be able to fly far enough to live in another wetland. Broads swallowtails are at high risk of extinction in the long term. But as things get warmer the less demanding swallowtail that lives on mainland Europe may take up residence in warmer southern areas, where plants of the carrot family provide food. It could be found on an allotment near you! Many areas of fen have been restored in the Broads as part of conservation management and the continuation of the thatching industry. Grazing by hardy ponies such as Koniks and Welsh ponies also provides a method of managing these areas on a large scale. The area of open fen in the Broads is about 1,800ha (or the size of the same number of football pitches), similar to the extent of open fen in 1946. In the summer of 2017, the swallowtail butterfly saw its highest recorded population levels since 2011, with a sixty-six percent increase in numbers between 1976 and 2015. The encouraging figures reflect the efforts of the organisations and landowners involved in conservation and biodiversity work. With the continuation of fen management, the Broads Authority and many others hope to retain the population of swallowtails for as long as possible. The Broads fens are also vital for the survival of many of the other sixty-five species of conservation concern that rely on the Broads for survival in the United Kingdom, including the Norfolk hawker dragonfly and crested buckler fern. For more swallowtail information, visit: *www.butterfly-conservation.org *www.norfolkwildlifetrust.org.uk Category:Transcripts